Solid metal block semiconductor light emitting device mounting substrates and packages

ABSTRACT

A mounting substrate for a semiconductor light emitting device includes a solid metal block having first and second opposing metal faces. The first metal face includes an insulating layer and a conductive layer on the insulating layer. The conductive layer is patterned to provide first and second conductive traces that connect to a semiconductor light emitting device. The second metal face may include heat sink fins therein. A flexible film including an optical element, such as a lens, also may be provided, overlying the semiconductor light emitting device.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of application Ser. No. 10/972,910,filed Oct. 25, 2004, entitled Solid Metal Block Semiconductor LightEmitting Device Mounting Substrates and Packages Including Cavities andHeat Sinks, assigned to the assignee of the present application, thedisclosure of which is hereby incorporated herein by reference in itsentirety as if set forth fully herein.

FIELD OF THE INVENTION

This invention relates to semiconductor light emitting devices andmanufacturing methods therefor, and more particularly to packaging andpackaging methods for semiconductor light emitting devices.

BACKGROUND OF THE INVENTION

Semiconductor light emitting devices, such as Light Emitting Diodes(LEDs) or laser diodes, are widely used for many applications. As iswell known to those having skill in the art, a semiconductor lightemitting device includes one or more semiconductor layers that areconfigured to emit coherent and/or incoherent light upon energizationthereof. It is also known that the semiconductor light emitting devicegenerally is packaged to provide external electrical connections, heatsinking, lenses or waveguides, environmental protection and/or otherfunctions.

For example, it is known to provide a two-piece package for asemiconductor light emitting device, wherein the semiconductor lightemitting device is mounted on a substrate that comprises alumina,aluminum nitride and/or other materials, which include electrical tracesthereon, to provide external connections for the semiconductor lightemitting device. A second substrate which may comprise silver platedcopper, is mounted on the first substrate, for example using glue,surrounding the semiconductor light emitting device. A lens may beplaced on the second substrate over the semiconductor light emittingdevice. Light emitting diodes with two-piece packages as described aboveare described in Application Serial No. US 2004/0041222 A1 to Loh,entitled Power Surface Mount Light Emitting Die Package, published Mar.4, 2004, assigned to the assignee of the present invention, thedisclosure of which is hereby incorporated herein by reference in itsentirety as if set forth fully herein.

SUMMARY OF THE INVENTION

Some embodiments of the present invention provide a mounting substratefor a semiconductor light emitting device that includes a solid metalblock having first and second opposing metal faces. The first metal faceincludes therein a cavity that is configured to mount at least onesemiconductor light emitting device therein and to reflect light that isemitted by at least one semiconductor light emitting device that ismounted therein away from the cavity. The second metal face includestherein a plurality of heat sink fins.

In some embodiments, a reflective coating is provided in the cavity. Inother embodiments, first and second conductive traces are provided inthe cavity that are configured to connect to at least one semiconductorlight emitting device that is mounted in the cavity. In yet otherembodiments, an insulating layer is provided on the first metal face,and a conductive layer is provided on the insulating layer that ispatterned to provide the reflective coating in the cavity and the firstand second conductive traces in the cavity. The solid metal block can bea solid aluminum block with an aluminum oxide insulating layer. In otherembodiments, the solid metal block is a solid steel block with a ceramicinsulating layer.

In still other embodiments of the invention, the first metal faceincludes a pedestal therein, and the cavity is in the pedestal. In yetother embodiments, the solid metal block includes a through hole thereinthat extends from the first face to the second face. The through holeincludes a conductive via therein that is electrically connected to thefirst or second conductive traces.

In some embodiments of the present invention, a semiconductor lightemitting device is mounted in the cavity. In other embodiments, a lensextends across the cavity. In still other embodiments, when the cavityis in a pedestal, the lens extends across the pedestal and across thecavity. In still other embodiments, a flexible film that includes anoptical element therein is provided on the first metal face, wherein theoptical element extends across the cavity or extends across the pedestaland across the cavity. Accordingly, semiconductor light emitting devicepackages may be provided.

Phosphor also may also be provided according to various elements of thepresent invention. In some embodiments, a coating including phosphor isprovided on the inner and/or outer surface of the lens or opticalelement. In other embodiments, the lens or optical element includesphosphor dispersed therein. In yet other embodiments, a phosphor coatingis provided on the semiconductor light emitting device itself.Combinations of these embodiments also may be provided.

An integrated circuit also may be provided on the solid metal block thatis electrically connected to the first and second traces. The integratedcircuit may be a light emitting device driver integrated circuit.Finally, an optical coupling medium may be provided in the cavity and atleast partially surrounding the light emitting device.

Other embodiments of the present invention provide a mounting substratefor an array of semiconductor light emitting devices. In theseembodiments, the first metal face includes therein a plurality ofcavities, a respective one of which is configured to mount at least onesemiconductor light emitting device therein, and to reflect light thatis emitted by the at least one semiconductor light emitting device thatis mounted therein away from the respective cavity. The second metalface includes a plurality of heat sink fins. A reflective coating,conductive traces, an insulating layer, pedestals, through holes,lenses, flexible films, optical elements, phosphor, integrated circuitsand/or optical coupling media also may be provided according to any ofthe embodiments that were described above, to provide semiconductorlight emitting device packages. Moreover, the cavities may be uniformlyand/or nonuniformly spaced apart from one another in the first face.

Semiconductor light emitting devices may be packaged according to someembodiments of the present invention by fabricating a solid metal blockincluding one or more cavities in a first face thereof and a pluralityof heat sink fins in a second face thereof, forming an insulating layeron the first face, forming a conductive layer and mounting asemiconductor light emitting device in at least one of the cavities.Pedestals, through holes, lenses, flexible films, optical elements,phosphor, integrated circuits and/or optical coupling media may beprovided according to any of the embodiments that were described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A-1H are side cross-sectional views of mounting substrates forsemiconductor light emitting devices according to various embodiments ofthe present invention.

FIG. 2 is a flowchart of steps that may be performed to fabricatemounting substrates for semiconductor light emitting devices accordingto various embodiments of the present invention.

FIGS. 3A and 3B are top and bottom perspective views of a semiconductorlight emitting device package according to various embodiments of thepresent invention.

FIG. 4 is an exploded perspective view of a packaged semiconductor lightemitting device according to various embodiments of the presentinvention.

FIG. 5 is an assembled perspective view of a packaged semiconductorlight emitting device according to various embodiments of the presentinvention.

FIGS. 6A-6H are cross-sectional views of transmissive optical elementsaccording to various embodiments of the present invention that may beused with semiconductor light emitting devices.

FIG. 7 is a cross-sectional view of a semiconductor light emittingdevice package according to other embodiments of the present invention.

FIG. 8 is a schematic diagram of a molding apparatus that may be used tofabricate optical elements according to embodiments of the presentinvention.

FIGS. 9 and 10 are flowcharts of steps that may be performed to packagesemiconductor light emitting devices according to various embodiments ofthe present invention.

FIGS. 11A and 11B, 12A and 12B, and 13A and 13B are cross-sectionalviews of semiconductor light emitting device packages duringintermediate fabrication steps according to various embodiments of thepresent invention.

FIG. 14 is an exploded cross-sectional view of a semiconductor lightemitting device package and fabrication methods therefor, according tovarious embodiments of the present invention.

FIGS. 15-25 are cross-sectional views of semiconductor light emittingdevice packages according to various embodiments of the presentinvention.

FIG. 26 is a perspective view of a semiconductor light emitting devicepackage according to various embodiments of the present invention.

FIG. 27 is a side cross-sectional view of a packaged semiconductor lightemitting device according to various embodiments of the presentinvention.

FIG. 28 is a perspective view of FIG. 27.

FIG. 29 is a side cross-sectional view of a packaged semiconductor lightemitting device according to other embodiments of the present invention.

FIG. 30 is a flowchart of steps that may be performed to packagesemiconductor light emitting devices according to various embodiments ofthe present invention.

DETAILED DESCRIPTION

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which embodiments of theinvention are shown. However, this invention should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will be thorough and complete, andwill fully convey the scope of the invention to those skilled in theart. In the drawings, the thickness of layers and regions areexaggerated for clarity. Like numbers refer to like elements throughout.As used herein the term “and/or” includes any and all combinations ofone or more of the associated listed items and may be abbreviated as“/”.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprises”and/or “comprising,” when used in this specification, specify thepresence of stated features, regions, steps, operations, elements,and/or components, but do not preclude the presence or addition of oneor more other features, regions, steps, operations, elements,components, and/or groups thereof.

It will be understood that when an element such as a layer or region isreferred to as being “on” or extending “onto” another element, it can bedirectly on or extend directly onto the other element or interveningelements may also be present. In contrast, when an element is referredto as being “directly on” or extending “directly onto” another element,there are no intervening elements present. It will also be understoodthat when an element is referred to as being “connected” or “coupled” toanother element, it can be directly connected or coupled to the otherelement or intervening elements may be present. In contrast, when anelement is referred to as being “directly connected” or “directlycoupled” to another element, there are no intervening elements present.

It will be understood that, although the terms first, second, etc. maybe used herein to describe various elements, components, regions, layersand/or sections, these elements, components, regions, layers and/orsections should not be limited by these terms. These terms are only usedto distinguish one element, component, region, layer or section fromanother region, layer or section. Thus, a first element, component,region, layer or section discussed below could be termed a secondelement, component, region, layer or section without departing from theteachings of the present invention.

Furthermore, relative terms, such as “lower”, “base”, or “horizontal”,and “upper”, “top”, or “vertical” may be used herein to describe oneelement's relationship to another element as illustrated in the Figures.It will be understood that relative terms are intended to encompassdifferent orientations of the device in addition to the orientationdepicted in the Figures. For example, if the device in the Figures isturned over, elements described as being on the “lower” side of otherelements would then be oriented on “upper” sides of the other elements.The exemplary term “lower”, can therefore, encompasses both anorientation of “lower” and “upper,” depending on the particularorientation of the figure. Similarly, if the device in one of thefigures is turned over, elements described as “below” or “beneath” otherelements would then be oriented “above” the other elements. Theexemplary terms “below” or “beneath” can, therefore, encompass both anorientation of above and below.

Embodiments of the present invention are described herein with referenceto cross section illustrations that are schematic illustrations ofidealized embodiments of the present invention. As such, variations fromthe shapes of the illustrations as a result, for example, ofmanufacturing techniques and/or tolerances, are to be expected. Thus,embodiments of the present invention should not be construed as limitedto the particular shapes of regions illustrated herein but are toinclude deviations in shapes that result, for example, frommanufacturing. For example, a region illustrated or described as flatmay, typically, have rough and/or nonlinear features. Moreover, sharpangles that are illustrated, typically, may be rounded. Thus, theregions illustrated in the figures are schematic in nature and theirshapes are not intended to illustrate the precise shape of a region andare not intended to limit the scope of the present invention.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this invention belongs. It will befurther understood that terms, such as those defined in commonly useddictionaries, should be interpreted as having a meaning that isconsistent with their meaning in the context of the relevant art andwill not be interpreted in an idealized or overly formal sense unlessexpressly so defined herein.

FIGS. 1A-1H are side cross-sectional views of mounting substrates forsemiconductor light emitting devices according to various embodiments ofthe present invention. Referring to FIG. 1A, mounting substrates forsemiconductor light emitting devices according to various embodiments ofthe invention include a solid metal block 100 having a cavity 110 in afirst metal face 100 a thereof, that is configured to mount asemiconductor light emitting device therein, and to reflect light thatis emitted by at least one semiconductor light emitting device that ismounted therein away from the cavity 110. In some embodiments, the solidmetal block 100 is a solid aluminum block or a solid steel block. Thecavity 110 may be formed by machining, coining, etching and/or otherconventional techniques. The size and shape of the cavity 110 may beconfigured to enhance or optimize the amount and/or direction of lightthat is reflected away from the cavity 110 from a semiconductor lightemitting device that is mounted in the cavity 110. For example, obliquesidewalls 110 a and or a semi-ellipsoidal cross-sectional profile may beprovided, so as to reflect light that is emitted by at least onesemiconductor light emitting device that is mounted therein away fromthe cavity 110. An additional reflective layer also may be provided onthe cavity sidewall and/or floor, as will be described below.

Still referring to FIG. 1A, the second metal face 100 b of the solidmetal block 100 includes a plurality of heat sink fins 190 therein. Thenumber, spacing and/or geometry of the heat sink fins 190 may be variedfor desired heat dissipation, as is well known to those having skill inthe art. Moreover, the heat sink fins need not be uniformly spaced, neednot be straight, need not be rectangular in cross-section, and can beprovided in a one-dimensional elongated array and/or in atwo-dimensional array of heat sink fin posts using techniques that arewell known to those having skill in the art. Each fin may itself includeone or more projecting fins thereon. In some embodiments, the metalblock 100 may be a rectangular solid metal block of aluminum or steelabout 6 mm×about 9 mm, and about 2 mm thick, and the cavity 110 may beabout 1.2 mm deep with a circular floor that is about 2.5 mm indiameter, with sidewalls 110 a that are of any simple or complex shapeto obtain desired radiation patterns. However, the block 100 may haveother polygonal and/or ellipsoidal shapes. Moreover, in someembodiments, an array of 12 heat sink fins 190 may be provided, whereinthe heat sink fins have a width of 2 mm, a pitch of 5 mm and a depth of9 mm. However, many other configurations of heat sink fins 190 may beprovided. For example, many heat sink design profiles may be found onthe Web at aavid.com.

FIG. 1B illustrates mounting substrates according to other embodimentsof the present invention. As shown in FIG. 1B, an electricallyinsulating coating 120 is provided on the surface of the solid metalblock 100. The insulating coating 120 may be provided on the entireexposed surface of the solid metal block, including the heat sink fins190, or excluding the heat sink fins 190 as shown in FIG. 1B, or on onlya smaller portion of the exposed surface of the solid metal block. Insome embodiments, as will be described below, the insulating coating 120includes a thin layer of aluminum oxide (Al₂O₃) that may be formed, forexample, by anodic oxidation of the solid metal block 100 in embodimentswhere the solid metal block 100 is aluminum. In other embodiments, theinsulating coating 120 includes a ceramic coating on a solid steel block100. In some embodiments, the coating 120 is sufficiently thick toprovide an electrical insulator, but is maintained sufficiently thin soas not to unduly increase the thermal conductive path therethrough.

Solid metal blocks 100 of aluminum including thin insulating coatings120 of aluminum oxide may be provided using substrates that are marketedby the IRC Advanced Film Division of TT Electronics, Corpus Christi,Tex., under the designation Anotherm™, that are described, for example,in brochures entitled Thick Film Application Specific Capabilities andInsulated Aluminium Substrates, 2002, both of which are available on theWeb at irctt.com. Moreover, solid metal blocks 100 of steel with aninsulating coating 120 of ceramic may be provided using substrates thatare marketed by Heatron Inc., Leavenworth, Kans., under the designationELPOR®, that are described, for example, in a brochure entitled MetalCore PCBs for LED Light Engines, available on the Web at heatron.com.Cavities 110 and heat sink fins 190 may be provided in these solid metalblocks according to any of the embodiments described herein. Other solidmetal blocks 100 with insulating coatings 120 may be provided with atleast one cavity 110 in a first metal face 100 a thereof, and aplurality of heat sink fins 190 in a second metal face 100 b thereof inother embodiments of the present invention.

Referring now to FIG. 1C, first and second spaced apart conductivetraces 130 a, 130 b are provided on the insulating coating 120 in thecavity 110. The first and second spaced apart conductive traces 130 a,130 b are configured to connect to a semiconductor light emitting devicethat is mounted in the cavity 110. As shown in FIG. 1C, in someembodiments, the first and second spaced apart conductive traces 130 aand 130 b can extend from the cavity 110 onto the first face 100 a ofthe solid metal block 100. When the insulating coating 120 is providedon only a portion of the solid metal block 100, it may be providedbetween the first and second spaced apart traces 130 a and 130 b and thesolid metal block 100, to thereby insulate the first and second metaltraces 130 a and 130 b from the solid metal block 100.

FIG. 1D illustrates other embodiments of the present invention whereinthe first and second spaced apart conductive traces 130 a′, 130 b′extend from the cavity 110 to the first face 100 a around at least oneside 100 c of the metal block and onto a second face 100 b of the metalblock that is opposite the first face 100 a. Thus, backside contacts maybe provided.

In some embodiments of the invention, the first and second spaced apartconductive traces 130 a, 130 b and/or 130 a′, 130 b′ comprise metal and,in some embodiments, a reflective metal such as silver. Thus, in someembodiments of the present invention, a conductive layer is provided onthe insulating layer 120 that is patterned to provide a reflectivecoating in the cavity 110 and first and second conductive traces 130 a,130 b that are configured to connect to at least one semiconductor lightemitting device that is mounted in the cavity 110.

In other embodiments, as shown in FIG. 1E, one or more separatereflective layers 132 a, 132 b may be provided on the spaced apartconductive traces 130 a′, 130 b′ and/or in the cavity 110. In theseembodiments, the conductive traces 130 a′, 130 b′ may comprise copper,and the reflective layers 132 a, 132 b may comprise silver. In contrast,in embodiments of FIGS. 1C and/or 1D, the conductive traces may comprisesilver to provide an integral reflector.

In still other embodiments, a separate reflector layer need not beprovided. Rather, the surface of the cavity 110 including the sidewall110 a may provide sufficient reflectance. Thus, the cavity 110 isconfigured geometrically to reflect light that is emitted by at leastone semiconductor light emitting device that is mounted therein, forexample, by providing oblique sidewall(s) 110 a, reflective obliquesidewall(s) 110 a and/or a reflective coating 132 a and/or 132 b on theoblique sidewall(s) 110 a and/or on the floor of the cavity 110, suchthat the dimensions and/or sidewall geometry of the cavity act toreflect light that is emitted by at least one semiconductor lightemitting device that is mounted in the cavity 110, away from the cavity110. Reflection may be provided or enhanced by the addition of areflective coating 132 a and/or 132 b in the cavity 110.

In still other embodiments of the present invention, as illustrated inFIG. 1F, backside contacts may be provided by providing first and/orsecond through holes 140 a and/or 140 b, which may be formed in thesolid metal block 100 by machining, etching and/or other conventionaltechniques. Moreover, as shown in FIG. 1F, the insulating coating 120extends into the through holes 140 a and 140 b. First and secondconductive vias 142 a, 142 b are provided in the first and secondthrough holes 140 a, 140 b, and are insulated from the solid metal block100 by the insulating coating 120 in through holes 140 a, 140 b.

In FIG. 1F, the through holes 140 a and 140 b, and the conductive vias142 a and 142 b extend from the cavity 110 to the second face 100 b. Thethrough holes 140 a, 140 b may be orthogonal and/or oblique to the firstand second faces 100 a, 100 b. First and second spaced apart conductivetraces 130 a′, 130 b′ may be provided in the cavity 110, andelectrically connected to the respective first and second conductivevias 142 a, 142 b. On the second face 100 b, third and fourth spacedapart conductive traces 130 c, 130 d also may be provided that areelectrically connected to the respective first and second conductivevias 142 a, 142 b. A solder mask layer may be provided in someembodiments to isolate the third and fourth conductive traces 130 e, 130d on the second face 100 b, to facilitate circuit board assembly. Soldermask layers are well known to those having skill in the art and need notbe described further herein. As shown in FIG. 1F, heat sink fins 190 maybe provided in the center and/or at the edges of the solid metal block100, i.e., adjacent the cavity 110 and/or offset from the cavity 110.

In embodiments of FIG. 1F, the first and second through holes 140 a, 140b and the first and second conductive vias 142 a, 142 b extended fromthe cavity 110 to the second face 100 b. In embodiments of FIG. 1G, thefirst and second through holes 140 a′, 140 b′ and the first and secondconductive vias 142 a′, 142 b′ extend from the first face 100 a outsidethe cavity 110 to the second face 100 b. The through holes 140 a′, 140b′ may be orthogonal and/or oblique to the first and second faces 100 a,100 b. First and second spaced apart conductive traces 130 a″, 130 b″extend from the cavity 110 to the respective first and second conductivevias 142 a′, 142 b′ on the first face 100 a. Third and fourth traces 130c′, 130 d′ are provided on the second face 110 b that electricallyconnect to the respective first and second conductive via 142 a′, 142b′. As shown in FIG. 1G, heat sink fins 190 may be provided in thecenter and/or at the edges of the solid metal block 100, i.e., adjacentthe cavity 110 and/or offset from the cavity 110.

FIG. 1H illustrates embodiments of the invention that were described inconnection with FIG. 1D, and which further include a semiconductor lightemitting device 150 that is mounted in the cavity and that is connectedto the first and second spaced apart electrical traces 130 a′, 130 b′.Moreover, FIG. 1H illustrates that in other embodiments, a lens 170extends across the cavity. In still other embodiments, an encapsulant160 is provided between the semiconductor light emitting device 150 andthe lens 170. The encapsulant 160 may comprise clear epoxy and canenhance optical coupling from the semiconductor light emitting device150 to the lens 170. The encapsulant 160 also may be referred to hereinas an optical coupling media. In some embodiments, a lens retainer 180is provided on the solid metal block 100, to hold the lens 170 acrossthe cavity 110. In other embodiments, the lens retainer 180 may not beused.

The semiconductor light emitting device 150 can comprise a lightemitting diode, laser diode and/or other device which may include one ormore semiconductor layers, which may comprise silicon, silicon carbide,gallium nitride and/or other semiconductor materials, a substrate whichmay comprise sapphire, silicon, silicon carbide, gallium nitride orother microelectronic substrates, and one or more contact layers whichmay comprise metal and/or other conductive layers. The design andfabrication of semiconductor light emitting devices are well known tothose having skill in the art.

For example, the light emitting device 150 may be gallium nitride basedLEDs or lasers fabricated on a silicon carbide substrate such as thosedevices manufactured and sold by Cree, Inc. of Durham, N.C. For example,the present invention may be suitable for use with LEDs and/or lasers asdescribed in U.S. Pat. Nos. 6,201,262, 6,187,606, 6,120,600, 5,912,477,5,739,554, 5,631,190, 5,604,135, 5,523,589, 5,416,342, 5,393,993,5,338,944, 5,210,051, 5,027,168, 5,027,168, 4,966,862 and/or 4,918,497,the disclosures of which are incorporated herein by reference as if setforth fully herein. Other suitable LEDs and/or lasers are described inpublished U.S. Patent Publication No. US 2003/0006418 A1 entitled GroupIII Nitride Based Light Emitting Diode Structures With a Quantum Welland Superlattice, Group III Nitride Based Quantum Well Structures andGroup III Nitride Based Superlattice Structures, published Jan. 9, 2003,as well as published U.S. Patent Publication No. US 2002/0123164 A1entitled Light Emitting Diodes Including Modifications for LightExtraction and Manufacturing Methods Therefor. Furthermore, phosphorcoated LEDs, such as those described in United States Patent ApplicationNo. US 2004/0056260 A1, published on Mar. 25, 2004, entitledPhosphor-Coated Light Emitting Diodes Including Tapered Sidewalls, andFabrication Methods Therefor, the disclosure of which is incorporated byreference herein as if set forth fully, may also be suitable for use inembodiments of the present invention.

The LEDs and/or lasers may be configured to operate such that lightemission occurs through the substrate. In such embodiments, thesubstrate may be patterned so as to enhance light output of the devicesas is described, for example, in the above-cited U.S. Patent PublicationNo. US 2002/0123164 A1.

It will be understood by those having skill in the art that, althoughthe embodiments of FIGS. 1A-1H have been illustrated as separateembodiments, various elements of FIGS. 1A-1H may be used together toprovide various combinations and/or subcombinations of elements. Thus,for example, the reflective layer 132 a, 132 b may be used in any of theembodiments shown, and the semiconductor light emitting device 150, lens170, encapsulant 160 and/or the lens retainer 180 may be used in any ofthe embodiments shown. Accordingly, the present invention should not belimited to the separate embodiments that are shown in FIGS. 1A-1H.

FIG. 2 is a flowchart of steps that may be performed to packagesemiconductor light emitting devices according to various embodiments ofthe present invention. Referring to FIG. 2, as shown at Block 210, asolid block, such as an aluminum or steel block 100 of FIGS. 1A-1H, isprovided including a cavity, such as cavity 110, in a face thereof, thatis configured to mount a semiconductor light emitting device therein andto reflect light that is emitted by at least one semiconductor lightemitting device that is mounted therein away from the cavity 110. Theblock 100 also includes therein a plurality of heat sink fins 190 on thesecond face 100 b thereof. As was described above, the cavity may beprovided by machining, coining, etching and/or other conventionaltechniques. The heat sink fins 190 may also be provided by these and/orother techniques. Moreover, in other embodiments, the solid metal blockmay also contain the first and second spaced apart through holes such asthrough holes 140 a, 140 b and/or 140 a′, 140 b′ that extendtherethrough, and which may be fabricated by machining, etching and/orother conventional techniques.

Referring again to FIG. 2, at Block 220, an insulating coating is formedon at least some of the surface of the solid metal block. In someembodiments, a solid aluminum block is oxidized. In other embodiments, aceramic coating is provided on a solid steel block. Other insulatingcoatings and other solid metal blocks may be provided. In someembodiments, the entire exposed surface of the solid metal block iscoated. Moreover, when through holes are provided, the inner surfaces ofthe through holes also may be coated. In other embodiments, onlyportions of the metal block are coated, for example, by providing amasking layer on those portions which are desired not to be coated.Oxidization of aluminum is well known to those having skill in the artand may be performed, for example, using an anodic oxidation processesand/or other oxidation processes, to provide a thin layer of Al₂O₃ onthe aluminum. Ceramic coatings on steel are also well known to thosehaving skill in the art and need not be described further herein.

Still referring to FIG. 2, at Block 230, first and second spaced apartconductive traces, such as traces 130 a, 130 b and/or 130 a′, 130 b′,are fabricated in the cavity on the first face, on the sides and/or onthe second face, depending on the configuration, as was described above.Moreover, in some embodiments, conductive vias, such as vias 142 a, 142b and/or 142 a′, 142 b′ may be fabricated in through holes. Theconductive vias and/or the reflector layer may be fabricated prior to,concurrent with and/or after the conductive traces. The fabrication ofconductive traces on a solid metal block that is coated with aninsulating layer is well known to provide circuit board-like structureswith an aluminum, steel and/or other core, and accordingly need not bedescribed in detail herein.

Finally, at Block 240, other operations are performed to mount thesemiconductor device, lens, flexible film encapsulant and/or retainer onthe substrate, as described herein. It also will be noted that in somealternate implementations, the functions/acts noted in the blocks ofFIG. 2 may occur out of the order noted in the flowchart. For example,two blocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality/acts involved.

FIGS. 3A and 3B are top and bottom perspective views, respectively, ofpackages according to embodiments of the present invention, which maycorrespond to the cross-sectional view of FIG. 1D. FIGS. 3A and 3Billustrate the solid metal block 100, the cavity 110, the fins 190, thefirst and second spaced apart conductive traces 130 a′, 130 b′ that wraparound the solid metal block, and the semiconductor light emittingdevice 150 mounted in the cavity 110. The insulating coating 120 may betransparent and is not shown. A second insulating layer and/or soldermask may be provided on the first and/or second spaced apart conductivetraces in these and/or any other embodiments.

FIG. 4 illustrates an exploded perspective view of other embodiments ofthe present invention, which may correspond to FIG. 1H. As shown in FIG.4, the solid metal block 100 includes a cavity 110 therein, and aplurality of spaced apart electrical traces thereon. In FIG. 4, thefirst electrical trace 130 a′ is shown. However, rather than a singlesecond electrical trace, a plurality of second electrical traces 330 a′,330 b′ and 330 c′ may be provided to connect to a plurality ofsemiconductor light emitting devices 150′ that may be mounted in thecavity 110 to provide, for example, red, green and blue semiconductorlight emitting devices for a white light source. The encapsulant 160 andlens retainer 180 are shown. Other configurations of lens retainers 180can provide a ridge and/or other conventional mounting means formounting a lens 170 on the solid metal block 100. It also will beunderstood that an epoxy or other glue may be used in a lens retainer180. The lens retainer 180 may also provide additional top heat sinkingcapabilities in some embodiments of the present invention. FIG. 5illustrates the assembled package of FIG. 4.

Accordingly, some embodiments of the present invention use a solid metalblock as a mounting substrate for a semiconductor light emitting deviceand include one or more integral cavities and a plurality of integralheat sink fins. Aluminum or steel have sufficient thermal conductivityto be used as an effective heat sink when integral fins are provided.Additionally, the cost of the material and the cost of fabrication canbe low. Moreover, the ability to grow high quality insulating oxidesand/or provide ceramic coatings allows the desired electrical traces tobe formed without a severe impact on the thermal resistance, since thethickness of the anodic oxidation or other coating can be preciselycontrolled. This insulating layer also can be selectively patterned,which can allow the addition of another plated metal to the substrate,such as plating silver on the cavity sidewalls only, for increasedoptical performance.

The ability to form an optical cavity and heat sink fins in the solidmetal block, rather than a separate reflector cup and a separate heatsink, can reduce the assembly cost, since the total number of elementsfor the package can be reduced. Additionally, the fact that thereflector (cavity) position is fixed with respect to the solid metalblock can also reduce the assembly complexity. Finally, the integralheat sink fins can enhance thermal efficiency. Embodiments of theinvention may be particularly useful for high power semiconductor lightemitting devices such as high power LEDs and/or laser diodes.

Other embodiments of solid metal block mounting substrates that may beused according to embodiments of the present invention are described inapplication Ser. No. 10/659,108, filed Sep. 9, 2003, entitled SolidMetal Block Mounting Substrates for Semiconductor Light EmittingDevices, and Oxidizing Methods For Fabricating Same, assigned to theassignee of the present invention, the disclosure of which is herebyincorporated herein by reference in its entirety as if set forth fullyherein.

It is often desirable to incorporate a phosphor into the light emittingdevice, to enhance the emitted radiation in a particular frequency bandand/or to convert at least some of the radiation to another frequencyband. Phosphors may be included in a light emitting device using manyconventional techniques. In one technique, phosphor is coated insideand/or outside a plastic shell of the device. In other techniques,phosphor is coated on the semiconductor light emitting device itself,for example using electrophoretic deposition. In still otherembodiments, a drop of a material such as epoxy that contains phosphortherein may be placed inside the plastic shell, on the semiconductorlight emitting device and/or between the device and the shell. LEDs thatemploy phosphor coatings are described, for example, in U.S. Pat. Nos.6,252,254; 6,069,440; 5,858,278; 5,813,753; 5,277,840; and 5,959,316.

Some embodiments of the present invention that will now be describedprovide a coating including phosphor on the lens. In other embodiments,the lens includes phosphor dispersed therein.

FIGS. 6A-6H are cross-sectional views of transmissive optical elementsaccording to various embodiments of the present invention. These opticalelements may be used to package semiconductor light emitting devices aswill also be described below.

As shown in FIG. 6A, transmissive optical elements according to someembodiments of the present invention include a lens 170 that comprisestransparent plastic. As used herein, the term “transparent” means thatoptical radiation from the semiconductor light emitting device can passthrough the material without being totally absorbed or totallyreflected. The lens 170 includes phosphor 610 dispersed therein. As iswell mown to those having skill in the art, the lens 170 may comprisepolycarbonate material and/or other conventional plastic materials thatare used to fabricate transmissive optical elements. Moreover, thephosphor 610 can comprise any conventional phosphor includingcerium-doped YAG and/or other conventional phosphors. In some specificembodiments, the phosphor comprises Cerium doped Yttrium Aluminum Garnet(YAG:Ce). In other embodiments, nano-phosphors may be used. Phosphorsare well known to those having skill in the art and need not bedescribed further herein.

In FIG. 6A, the phosphor 610 is uniformly dispersed within the lens 170.In contrast, in FIG. 6B, the phosphor 620 is nonuniformly dispersed inthe lens 170. Various patterns of phosphor 620 may be formed, forexample, to provide areas of higher intensity and/or different colorand/or to provide various indicia on the lens 170 when illuminated. InFIGS. 6A-6B, the lens 110 is a dome-shaped lens. As used herein, theterms “dome” and “dome-shaped” refer to structures having a generallyarcuate surface profile, including regular hemispherical structures aswell as other generally arcuate structures that do not form a regularhemisphere, which are eccentric in shape and/or have other features,structures and/or surfaces.

Referring now to FIG. 6C, one or more coatings 630 may be provided onthe outside of the lens 170. The coating may be a protective coating, apolarizing coating, a coating with indicia and/or any other conventionalcoating for an optical element that is well known to those having skillin the art. In FIG. 6D, one or more inner coatings 640 is provided onthe inner surface of the lens 170. Again, any conventional coating orcombination of coatings may be used.

Moreover, other embodiments of the invention provide both an inner andan outer coating for the lens 170 that includes uniformly distributedphosphor 610 and/or nonuniformly distributed phosphor 620 therein. Byproviding an inner and outer coating, improved index matching to thephosphor may be provided. Thus, three layers may be injection moldedaccording to some embodiments of the present invention. Otherembodiments of the present invention can use an index matching media,such as a liquid and/or solid gel, within the shell, to assist in indexmatching. The use of inner and outer layers can reduce the number ofphotons that can be trapped in the phosphor-containing layer due toindex matching issues.

FIG. 6E describes other embodiments of the present invention wherein atransparent inner core 650 is provided inside the lens 170. In someembodiments, as also shown in FIG. 6E, the transparent inner core 650fills the lens 170, to provide a hemispherical optical element. Thetransparent inner core 650 may be uniformly transparent and/or mayinclude translucent and/or opaque regions therein. The transparent innercore 650 may comprise glass, plastic and/or other optical couplingmedia.

FIG. 6F illustrates other embodiments of the present invention wherein aphosphor-containing lens 170 is combined with a semiconductor lightemitting device 150 that is configured to emit light 662 into andthrough the transparent inner core 650 and through the lens 170, toemerge from the lens 170.

FIG. 6G is a cross-sectional view of other embodiments of the presentinvention. As shown in FIG. 6G, a mounting substrate 100 is provided,such that the light emitting device 150 is between the mountingsubstrate 100 and the transparent inner core 650. As also shown in FIG.6G, the mounting substrate 100 includes a cavity 110 therein and thelight emitting device 150 is at least partially in the cavity 110. Heatsink fins 190 also are provided.

FIG. 6H illustrates yet other embodiments of the present invention. Inthese embodiments, the cavity 110 may be filled with an encapsulant 680,such as epoxy and/or other optical coupling media (e.g., silicon). Theencapsulant 680 can enhance optical coupling from the light emittingdevice 150 to the transparent inner core 650. Heat sink fins 190 alsoare provided.

It will be understood by those having skill in the art that, althoughthe embodiments of FIGS. 6A-6H have been illustrated as separateembodiments, various elements of FIGS. 6A-6H may be used together invarious combinations and subcombinations of elements. Thus, for example,combinations of inner and outer coatings 640 and 630, uniformlydistributed phosphor 610 and nonuniformly distributed phosphor 620,light emitting devices 150, mounting substrates 100, cavities 110, innercores 650 and encapsulant 680 may be used together. Moreover,embodiments of FIGS. 6A-6H may be combined with any other embodimentsdisclosed herein.

FIG. 7 is a cross-sectional view of light emitting devices according toother embodiments of the present invention. As shown in FIG. 7, theseembodiments include a lens 170 which may be made of opticallytransparent material that is loaded with phosphor and/or otherchemicals. An inner core 650 may be made of optically transparentmaterial such as plastic or glass and may be placed on anencapsulating-containing cavity 110 in a mounting substrate 100including heat sink fins 190. The lens 170 and the inner core 650 form acomposite lens for a light emitting diode 150.

FIG. 8 is a schematic block diagram of an apparatus for formingtransmissive optical elements according to various embodiments of thepresent invention. In particular, FIG. 8 illustrates an injectionmolding apparatus that may be used to form transmissive optical elementsaccording to various embodiments of the present invention. As shown inFIG. 8, an injection molding apparatus includes a hopper 810 or otherstorage device in which a transparent plastic and/or phosphor additive850 are provided. The transparent plastic and/or phosphor additive maybe provided in pellet, powder and/or solid form. Other additives, suchas solvents, binders, etc. may be included, as is well known to thosehaving skill in the art. An injector 820 may include a heater and ascrew mechanism that is used to melt the transparent plastic andphosphor additive and/or maintain these materials in a melted state, toprovide a molten liquid that comprises transparent plastic and thephosphor additive. The injector 820 injects the molten liquid into amold 840 via nozzle 830. The mold 840 includes an appropriate channel860 therein, which can be used to define the shape of the opticalelement, such as a dome or keypad key. Injection molding of opticalelements is well known to those having skill in the art and isdescribed, for example, in U.S. Pat. Nos. 4,826,424; 5,110,278;5,882,553; 5,968,422; 6,156,242 and 6,383,417, and need not be describedin further detail herein. It also will be understood that castingtechniques also may be used, wherein molten liquid that comprises atransparent plastic and a phosphor additive is provided in a female moldwhich is then coupled to a male mold (or vice versa) to cast the opticalelement. Casting of optical elements is described, for example, in U.S.Pat. Nos. 4,107,238; 4,042,552; 4,141,941; 4,562,018; 5,143,660;5,374,668; 5,753,730 and 6,391,231, and need not be described in furtherdetail herein.

FIG. 9 is a flowchart of steps that may be used to package semiconductorlight emitting devices according to various embodiments of the presentinvention. As shown in FIG. 9, at Block 910, a mold, such as mold 840 ofFIG. 8, is filled with molten liquid that comprises a transparentplastic and a phosphor additive. At Block 920, the molten liquid isallowed to solidify to produce the optical element having phosphordispersed therein. The optical element is then removed from the mold andmounted across a cavity in a solid metal block.

FIG. 10 is a flowchart of steps that may be performed to packagesemiconductor light emitting devices according to embodiments of thepresent invention. As shown in FIG. 10 at Block 1010, a lens, such as adome-shaped lens 170, that comprises a transparent plastic including aphosphor dispersed therein, is molded using injection molding, castingand/or other conventional techniques. At Block 1020, a core such as acore 650 of FIG. 6E is formed. It will be understood that, in someembodiments, the core 650 is placed or formed inside the lens 170,whereas, in other embodiments, Block 1020 precedes Block 1010 by forminga transparent core 650 and filling a mold that includes a transparentcore 650 with a molten liquid that comprises a transparent plastic and aphosphor additive, to form the lens 170 around the transparent core.

Still referring to FIG. 10, a semiconductor light emitting device, suchas device 150, is placed in a reflective cavity 110 of a mountingsubstrate such as mounting substrate 100. At Block 1040, an encapsulant,such as encapsulant 680 of FIG. 6H, is applied to the mounting substrate100, the light emitting device 150 and/or the core 650. Finally, atBlock 1050, the lens or shell is mated to the mounting substrate usingan epoxy, a snap-fit and/or other conventional mounting techniques.

It may be desirable for the inner core 650 to fill the entire lens, soas to reduce or minimize the amount of encapsulant 680 that may be used.As is well known to those having skill in the art, the encapsulant 680may have a different thermal expansion coefficient than the mountingsubstrate 100 and/or the inner core 650. By reducing or minimizing theamount of encapsulant 680 that is used at Block 1040, the effect ofthese thermal mismatches can be reduced or minimized.

It should also be noted that in some alternate implementations, thefunctions/acts noted in the blocks of FIGS. 9 and/or 10 may occur out ofthe order noted in the flowcharts. For example, two blocks shown insuccession may in fact be executed substantially concurrently or theblocks may sometimes be executed in the reverse order, depending uponthe functionality/acts involved.

Accordingly, some embodiments of the present invention can form acomposite optical element such as a lens using molding or castingtechniques. In some embodiments, injection molding can be used to placea phosphor layer dispersed in the molding material on the inner or outersurface and then completing the molding or casting process in theremaining volume, to form a desired optical element. These opticalelements can, in some embodiments, convert a blue light emitting diodebehind the lens, to create the appearance of white light.

Other embodiments of the present invention may use the phosphor toevenly disperse the light and/or to disperse the light in a desiredpattern. For example, conventional light emitting devices may emit lightin a “Batwing” radiation pattern, in which greater optical intensity isprovided at off-axis angles, such as angles of about 40° off-axis,compared to on-axis (0°) or at the sides (for example, angles greaterthan about 40°). Other light emitting diodes may provide a “Lambertian”radiation pattern, in which the greatest intensity is concentrated in acentral area to about 40° off-axis and then rapidly drops off at largerangles. Still other conventional devices may provide a side emittingradiation pattern, wherein the greatest light intensity is provided atlarge angles, such as 90° from the axis, and falls rapidly at smallerangles approaching the axis. In contrast, some embodiments of thepresent invention can reduce or eliminate angular-dependent radiationpatterns of light output from a light emitting device, such as angulardependence of Color Correlated Temperature (CCT). Thus, light intensityand the x,y chromaticity values/coordinates from all surfaces of thelens can remain relatively constant in some embodiments. This may beadvantageous when used for illumination applications, such as a roomwhere a spotlight effect is not desirable.

Injection molding processes as described above, according to someembodiments of the invention, can allow formation of a single opticalelement with multiple features, such as lensing and white conversion.Additionally, by using a two-molding or casting technique, according tosome embodiments, one can shape the phosphor layer to its desiredconfiguration, to reduce or minimize the angular dependence of colortemperature with viewing angle.

Other embodiments of lenses including phosphor dispersed therein aredescribed in application Ser. No. 10/659,240, filed Sep. 9, 2003,entitled Transmissive Optical Elements Including Transparent PlasticShell Having a Phosphor Dispersed Therein, and Methods of FabricatingSame, assigned to the assignee of the present invention, the disclosureof which is hereby incorporated by reference in its entirety as if setforth fully herein.

In other embodiments of the present invention, a coating includingphosphor is provided on the semiconductor light emitting device 150itself. In particular, it may be desirable to provide a phosphor for anLED, for example to provide solid-state lighting. In one example, LEDsthat are used for solid-state white lighting may produce high radiantflux output at short wavelengths, for example in the range of about 380nm to about 480 nm. One or more phosphors may be provided, wherein theshort wavelength, high energy photon output of the LED is used to excitethe phosphor, in part or entirely, to thereby down-convert in frequencysome or all of the LED's output to create the appearance of white light.

As one specific example, ultraviolet output from an LED at about 390 nmmay be used in conjunction with red, green and blue phosphors, to createthe appearance of white light. As another specific example, blue lightoutput at about 470 nm from an LED may be used to excite a yellowphosphor, to create the appearance of white light by transmitting someof the 470 nm blue output along with some secondary yellow emissionoccurring when part of the LEDs output is absorbed by the phosphor.

Phosphors may be included in a semiconductor light emitting device usingmany conventional techniques. In one technique, phosphor is coatedinside and/or outside the plastic shell of an LED. In other techniques,phosphor is coated on the semiconductor light emitting device itself,for example using electrophoretic deposition. In still other techniques,a drop of a material, such as epoxy that contains phosphor therein, maybe placed inside the plastic shell, on the semiconductor light emittingdevice and/or between the device and the shell. This technique may bereferred to as a “glob top”. The phosphor coatings may also incorporatean index matching material and/or a separate index matching material maybe provided.

Moreover, as was described above, published United States PatentApplication No. US 2004/0056260 A1 describes a light emitting diode thatincludes a substrate having first and second opposing faces and asidewall between the first and second opposing faces that extends at anoblique angle from the second face towards the first face. A conformalphosphor layer is provided on the oblique sidewall. The oblique sidewallcan allow more uniform phosphor coatings than conventional orthogonalsidewalls.

Semiconductor light emitting devices are fabricated, according to otherembodiments of the present invention, by placing a suspension comprisingphosphor particles suspended in solvent on at least a portion of a lightemitting surface of a semiconductor light emitting device, andevaporating at least some of the solvent to cause the phosphor particlesto deposit on at least a portion of the light emitting surface. Acoating comprising phosphor particles is thereby formed on at least aportion of the light emitting surface.

As used herein, a “suspension” means a two-phase solid-liquid system inwhich solid particles are mixed with, but undissolved (“suspended”), inliquid (“solvent”). Also, as used herein, a “solution” means asingle-phase liquid system in which solid particles are dissolved inliquid (“solvent”).

FIG. 11A is a cross-sectional view of a semiconductor light emittingdevice package during an intermediate fabrication step according tovarious embodiments of the present invention. As shown in FIG. 11A, asuspension 1120 including phosphor particles 1122 suspended in solvent1124 is placed on at least a portion of a light emitting surface 150 aof a semiconductor light emitting device 150. As used herein, “light”refers to any radiation, visible and/or invisible (such as ultraviolet)that is emitted by a semiconductor light emitting element 150. At leastsome of the solvent 1124 is then evaporated, as shown by the arrowlinking FIGS. 11A and 11B, to cause the phosphor particles 1122 todeposit on at least the portion of the light emitting surface 150 a, andform a coating 1130 thereon including the phosphor particles 1122. Insome embodiments, the suspension 1120 including phosphor particles 1122suspended in solvent 1124 is agitated while performing the placing ofFIG. 11A and/or while performing the evaporating. Moreover, as shown inFIG. 11B, evaporating can be performed to cause the phosphor particles122 to uniformly deposit on at least the portion of the light emittingsurface 150 a, to thereby form a uniform coating 1130 of the phosphorparticles 1122. In some embodiments, the phosphor particles 1122uniformly deposit on all the light emitting surface 150 a. Moreover, insome embodiments, substantially all of the solvent 1124 can beevaporated. For example, in some embodiments, at least about 80% of thesolvent can be evaporated. In some embodiments, substantially all thesolvent 1124 is evaporated to cause the phosphor particles 1122 touniformly deposit on all the light emitting surface 150 a.

In some embodiments of the present invention, the solvent 1124 comprisesMethyl Ethyl Ketone (MEK), alcohol, toluene, Amyl Acetate and/or otherconventional solvents. Moreover, in other embodiments, the phosphorparticles 1122 may be about 3-4 μm in size, and about 0.2 gm of thesephosphor particles 1122 may be mixed into about Sec of MEK solvent 1124,to provide the suspension 1120. The suspension 1120 may be dispensed viaan eyedropper pipette, and evaporation may take place at roomtemperature or at temperatures above or below room temperature, such asat about 60° C. and/or at about 100° C.

Phosphors also are well known to those having skill in the art. As usedherein, the phosphor particles 1122 may be Cerium-doped Yttrium AluminumGarnet (YAG:Ce) and/or other conventional phosphors and may be mixedinto the solvent 1124 using conventional mixing techniques, to therebyprovide the suspension 1120 comprising phosphor particles 1122. In someembodiments, the phosphor is configured to convert at least some lightthat is emitted from the light emitting surface 150 a such that lightthat emerges from the semiconductor light emitting device appears aswhite light.

FIG. 12A is a cross-sectional view of other embodiments of the presentinvention. As shown in FIG. 12A, a mounting substrate 100 is provided,and the semiconductor light emitting element 150 is mounted in a cavity110 therein. Heat sink fins 190 also are provided. The suspension 1120including phosphor particles 1122 suspended in solvent 1124 is placed inthe cavity 110. Thus, the cavity 110 can be used to confine thesuspension 1120 and thereby provide a controlled amount and geometry forthe suspension 1120.

Referring now to FIG. 12B, evaporation is performed, to therebyevaporate at least some of the solvent 1124 to cause the phosphorparticles 1122 to deposit on at least a portion of the light emittingsurface 150 a, and form a coating 1130 including the phosphor particles1122.

FIGS. 13A and 13B illustrate other embodiments of the present invention.As shown in FIG. 13A, in these embodiments, the cavity 110 includes acavity floor 110 b, and the semiconductor light emitting device 150 ismounted on the cavity floor 110 b. Moreover, the semiconductor lightemitting device 150 protrudes away from the cavity floor 110 b. In someembodiments, the light emitting surface 150 a of the semiconductor lightemitting device 150 includes a face 150 b that is remote from the cavityfloor 110 b, and a sidewall 150 c that extends between the face 150 band the cavity floor 110 b. As shown in FIG. 13B, evaporating isperformed to evaporate at least some of the solvent 1124, to cause thephosphor particles 1122 to uniformly deposit on at least a portion ofthe light emitting surface 150 a and thereby form a coating 1130 ofuniform thickness comprising the phosphor particles 1122. As also shownin FIG. 13B, in some embodiments, the coating may be of uniformthickness on the face 150 b and on the sidewall 150 c. In someembodiments, the coating 1130 may extend uniformly on the floor 110 boutside the light emitting element 150. In other embodiments, thecoating 1130 also may extend at least partially onto sidewalls 110 a ofthe cavity 110.

In other embodiments of the present invention, a binder may be added tothe suspension 1120 so that, upon evaporation, the phosphor particles1122 and the binder deposit on at least the portion of the lightemitting surface 150 a, and form a coating thereon comprising thephosphor particles 1122 and the binder. In some embodiments, a cellulosematerial, such as ethyl cellulose and/or nitro cellulose, may be used asa binder. Moreover, in other embodiments, at least some of the bindermay evaporate along with the solvent.

In other embodiments of the present invention, the suspension 1120includes the phosphor particles 1122 and light scattering particlessuspended in solvent 1124, and wherein at least some of the solvent 1124is evaporated to cause the phosphor particles 1122 and the lightscattering particles to deposit on at least a portion of the lightemitting device 150, and form a coating 1130 including the phosphorparticles 1122 and the light scattering particles. In some embodiments,the light scattering particles may include SiO₂ (glass) particles. Byselecting the size of the scattering particles, blue light may beeffectively scattered to make the emission source (for whiteapplications) more uniform (more specifically, random), in someembodiments.

It will also be understood that combinations and subcombinations ofembodiments of FIGS. 11A-13B also may be provided, according to variousembodiments of the invention. Moreover, combinations and subcombinationsof embodiments of FIGS. 11A-13B with any or all of the other figuresalso may be provided according to various embodiments of the invention.Other embodiments of coating a semiconductor light emitting device byevaporating solvents from a suspension are described in application Ser.No. 10/946,587, filed Sep. 21, 2004, entitled Methods of CoatingSemiconductor Light Emitting Elements by Evaporating Solvent From aSuspension, assigned to the assignee of the present invention, thedisclosure of which is hereby incorporated herein by reference in itsentirety as if set forth fully herein. Other embodiments of coating asemiconductor light emitting device by coating a patternable filmincluding transparent silicone and phosphor on a semiconductor lightemitting device are described in application Ser. No. 10/947,704, filedSep. 23, 2004, entitled Semiconductor Light Emitting Devices IncludingPatternable Films Comprising Transparent Silicone and Phosphor, andMethods of Manufacturing Same, assigned to the assignee of the presentinvention, the disclosure of which is hereby incorporated herein byreference in its entirety as if set forth fully herein.

Other embodiments of the invention provide a flexible film that includesan optical element therein on the first metal face, wherein the opticalelement extends across the cavity. In some embodiments, the opticalelement is a lens. In other embodiments, the optical element may includea phosphor coating and/or may include phosphor dispersed therein.

FIG. 14 is an exploded cross-sectional view of semiconductor lightemitting device packages and assembling methods therefor, according tovarious embodiments of the present invention. Referring to FIG. 14,these semiconductor light emitting device packages include a solid metalblock 100 having a first face 100 a including a cavity 110 therein, anda second face 100 b, including a plurality of heat sink fins 190therein. A flexible film 1420, including therein an optical element1430, is provided on the first face 100 a, and a semiconductor lightemitting device 150 is provided between the metal block 100 and theflexible film 1120, and configured to emit light 662 through the opticalelement. An attachment element 1450 may be used to attach the flexiblefilm 1420 and the solid metal block 100 to one another.

Still referring to FIG. 14, the flexible film 1420 can provide a coverslip that can be made of a flexible material such as a conventional RoomTemperature Vulcanizing (RTV) silicone rubber. Other silicone-basedand/or flexible materials may be used. By being made of a flexiblematerial, the flexible film 1420 can conform to the solid metal block100 as it expands and contracts during operations. Moreover, theflexible film 1420 can be made by simple low-cost techniques such astransfer molding, injection molding and/or other conventional techniquesthat are well known to those having skill in the art.

As described above, the flexible film 1420 includes therein an opticalelement 1430. The optical element can include a lens, a prism, anoptical emission enhancing and/or converting element, such as aphosphor, an optical scattering element and/or other optical element.One or more optical elements 1430 also may be provided, as will bedescribed in detail below. Moreover, as shown in FIG. 14, an opticalcoupling media 1470, such as an optical coupling gel and/or other indexmatching material, may be provided between the optical element 1430 andthe semiconductor light emitting device 150, in some embodiments.

Still referring to FIG. 14, the attachment element 1450 can be embodiedas an adhesive that may be placed around the periphery of the solidmetal block 100, around the periphery of the flexible film 1420 and/orat selected portions thereof, such as at the corners thereof. In otherembodiments, the solid metal block 100 may be coined around the flexiblefilm 1420, to provide an attachment element 1450. Other conventionalattaching techniques may be used.

FIG. 14 also illustrates methods of assembling or packagingsemiconductor light emitting devices according to various embodiments ofthe present invention. As shown in FIG. 14, a semiconductor lightemitting element 150 is mounted in a cavity 110 in a first face 100 a ofa solid metal block 100 that includes fins 190 on a second face 100 bthereof. A flexible film 1420 that includes therein an optical element1430 is attached to the first face 100 a, for example using anattachment element 1450, such that, in operation, the semiconductorlight emitting device 150 emits light 662 through the optical element1430. In some embodiments, an optical coupling media 1470 is placedbetween the semiconductor light emitting device 150 and the opticalelement 1430.

FIG. 15 is a cross-sectional view of packaged semiconductor lightemitting devices of FIG. 14, according to other embodiments of thepresent invention. The flexible film 1420 extends onto the face 100 abeyond the cavity 110. The optical element 1430 overlies the cavity 110,and the semiconductor light emitting device 150 is in the cavity 110,and is configured to emit light 662 through the optical element 1430. InFIG. 15, the optical element 1430 includes a concave lens. In someembodiments, an optical coupling media 1470 is provided in the cavity110 between the optical element 1430 and the semiconductor lightemitting device 150. In some embodiments, the optical coupling media1470 fills the cavity 110.

FIG. 16 is a cross-sectional view of other embodiments of the presentinvention. As shown in FIG. 16, two optical elements 1430 and 1630 areincluded in the flexible film 1420. A first optical element 1430includes a lens and a second optical element 1630 includes a prism.Light from the semiconductor light emitting device 150 passes throughthe prism 1630 and through the lens 1430. An optical coupling media 1470also may be provided. In some embodiments, the optical coupling media1470 fills the cavity 110. The optical coupling media 1470 may have asufficient difference in index of refraction from the prism 1630 suchthat the prism 1630 can reduce shadowing. As shown in FIG. 16, thesemiconductor light emitting device 150 includes a wire 1650 thatextends towards the flexible film 1420, and the prism 1630 is configuredto reduce shadowing by the wire 1650 of the light that is emitted fromthe semiconductor light emitting device 150. More uniform lightemissions thereby may be provided, with reduced shadowing of the wire1650. It will be understood that the term “wire” is used herein in ageneric sense to encompass any electrical connection for thesemiconductor light emitting device 150.

FIG. 17 is a cross-sectional view of other embodiments of the presentinvention. As shown in FIG. 17, phosphor 1710 is provided on theflexible film 1320 between the lens 1430 and the semiconductor lightemitting device 150. The phosphor 410 can include cerium-doped YttriumAluminum Garnet (YAG) and/or other conventional phosphors. In someembodiments, the phosphor comprises Cerium doped Yttrium Aluminum Garnet(YAG:Ce). In other embodiments, nano-phosphors may be used. Phosphorsare well known to those having skill in the art and need not bedescribed further herein. An optical coupling media 1470 also may beprovided that may fill the cavity 110.

FIG. 18 illustrates yet other embodiments of the present invention. Inthese embodiments, the lens 1430 includes a concave inner surface 1430 aadjacent the semiconductor light emitting device 150, and the phosphor1710 includes a conformal phosphor layer on the concave inner surface1430 a. An optical coupling media 1470 also may be provided that mayfill the cavity 110.

FIG. 19 is a cross-sectional view of other embodiments. As shown in FIG.19, at least a portion 1420 d of the flexible film 1420 that overliesthe cavity 110 is transparent to the light. Moreover, at least a portion1420 c of the flexible film 1420 that extends onto the face 100 a beyondthe cavity 110 is opaque to the light, as shown by the dotted portions1420 c of the flexible film 1420. The opaque regions 1420 c can reduceor prevent bouncing of light rays, and thereby potentially produce amore desirable light pattern. An optical coupling media 1470 also may beprovided that may fill the cavity 110.

FIG. 20 is a cross-sectional view of other embodiments of the presentinvention wherein the flexible film 1420 may be fabricated of multiplematerials. As shown in FIG. 20, at least a portion 1420 d of theflexible film 1420 that overlies the cavity 110 includes a firstmaterial, and at least a portion 1420 c of the flexible film 1420 thatextends onto the face 100 a beyond the cavity 110 includes a secondmaterial. Two or more materials may be used in the flexible film 1420 insome embodiments, to provide different characteristics for the portionof the flexible film 1420 through which light is emitted and throughwhich light is not emitted. Multiple materials may be used for otherpurposes in other embodiments. For example, an inflexible and/orflexible plastic lens may be attached to a flexible film. Such aflexible film 1420 with multiple materials may be fabricated usingconventional multiple molding techniques, for example. In someembodiments, the first material that is molded may not be fully cured,so as to provide a satisfactory bond that attaches to the secondmaterial that is subsequently molded. In other embodiments, the samematerial may be used for the optical element and the flexible film,wherein the optical element is formed and then the flexible film isformed surrounding the optical element. An optical coupling media 1470also may be provided that may fill the cavity 110.

FIG. 21 is a cross-sectional view of other embodiments of the presentinvention. In these embodiments, the semiconductor light emittingelement 150 includes a wire 1650, that extends towards and contacts theflexible film 1420 in the cavity 110. The flexible film 1420 includes atransparent conductor 2110 which can include Indium Tin Oxide (ITO)and/or other conventional transparent conductors. The transparentconductor 2110 extends in the cavity 110 and electrically connects tothe wire. Reduced shadowing by the wire 1650 thereby may be provided.Moreover, a wire bond to the metal block 100, and the potentialconsequent light distortion, may be reduced or eliminated. An opticalcoupling media 1470 also may be provided that may fill the cavity 110.

FIG. 22 is a cross-sectional view of other embodiments of the presentinvention. As shown in FIG. 22, the optical element 1430 includes a lensthat overlies the cavity 110 and protrudes away from the cavity 110. Theflexible film 1420 further includes a protruding element 2230 betweenthe lens 1430 and the light emitting element 150 that protrudes towardsthe cavity 110. As shown in FIG. 22, a conformal phosphor layer 1710 isprovided on the protruding element 2230. By providing the protrudingelement 2230 on the back of the lens 1430, optical coupling media 1470in the device may be displaced. Arrangements of FIG. 22 may thus providemore uniform phosphor coating at desired distances from the lightemitting element 150, so as to provide more uniform illumination. Theoptical coupling media 1470 may fill the cavity 110.

FIGS. 23 and 24 illustrate packages including multiple semiconductorlight emitting devices and/or multiple optical elements according tovarious embodiments of the present invention. For example, as shown inFIG. 23, the optical element 1430 is a first optical element, and thesemiconductor light emitting device 150 is a first semiconductor lightemitting device. The flexible film 1420 also includes therein a secondoptical element 1430′ that is spaced apart from the first opticalelement 1430, and the device further includes a second semiconductorlight emitting device 150′ between the substrate 100 and the flexiblefilm 1420, and configured to emit light through the second opticalelement 1430′. Moreover, a third optical element 1430″ and a thirdsemiconductor light emitting device 150″ also may be provided. Theoptical elements 1430, 1430′ and 1430″ may be the same and/or differentfrom one another, and the semiconductor light emitting devices 150, 150′and 150″ may be the same and/or different from one another. Moreover, inembodiments of FIG. 23, the cavity 110 is a first cavity, and second andthird cavities 110′, 110″, respectively, are provided for the second andthird semiconductor light emitting devices 150′, 150″, respectively. Thecavities 110, 110′ and 110″ may be the same and/or may have differentconfigurations from one another. An optical coupling media 1470 also maybe provided that may fill the cavity or cavities. It will be understoodthat larger or smaller numbers of semiconductor light emitting devicesand/or cavities may be provided in other embodiments.

As also shown in FIG. 23, the phosphor 1710 may be a first phosphorlayer, and second and/or third phosphor layers 1710′ and 1710″,respectively, may be provided on the flexible film 1420 between thesecond optical element 1430′ and the second semiconductor light emittingdevice 150′, and between the third optical element 1430″ and the thirdsemiconductor light emitting device 150″, respectively. The phosphorlayers 1710, 1710′, 1710″ may be the same, may be different and/or maybe eliminated. In particular, in some embodiments of the presentinvention, the first phosphor layer 1710 and the first semiconductorlight emitting device 150 are configured to generate red light, thesecond phosphor layer 1710′ and the second semiconductor light emittingdevice 150′ are configured to generate blue light, and the thirdphosphor layer 1710″ and the third semiconductor light emitting device150″ are configured to generate green light. A Red, Green, Blue (RGB)light emitting element that can emit white light thereby may be providedin some embodiments.

FIG. 24 is a cross-sectional view of other embodiments of the presentinvention. In these embodiments, a single cavity 2400 is provided forthe first, second and third semiconductor light emitting devices 150,150′ and 150″, respectively. An optical coupling media 1470 also may beprovided that may fill the cavity 2400. It will be understood thatlarger or smaller numbers of semiconductor light emitting devices and/orcavities may be provided in other embodiments.

FIG. 25 is a cross-sectional view of yet other embodiments of thepresent invention. In FIG. 25, the optical element 2530 comprises a lenshaving phosphor dispersed therein. Many embodiments of lenses includingphosphor dispersed therein were described above and need not berepeated. In still other embodiments of the present invention, anoptical scattering element may be embedded in the lens as shown in FIG.25, and/or provided as a separating layer as shown, for example, in FIG.22, in addition or instead of phosphor.

FIG. 26 is a perspective view of a semiconductor light emitting devicepackage according to other embodiments of the present invention.

It will be understood by those having skill in the art that variousembodiments of the invention have been described individually inconnection with FIGS. 14-26. However, combinations and subcombinationsof the embodiments of FIGS. 14-26 may be provided according to variousembodiments of the present invention, and also may be combined withembodiments according to any of the other figures described herein.

FIG. 27 is a cross-sectional view of a semiconductor light emittingdevice package according to various embodiments of the presentinvention. As shown in FIG. 27, a solid metal block 100 includes aplurality of cavities 110 in a first metal face 100 a thereof, and aplurality of heat sink fins 190 in a second metal face 100 b thereof. Aninsulating layer 120 is provided on the first metal face 100 a. Aconductive layer 130 is provided on the insulating layer, and ispatterned to provide a reflective coating 2730 a in the cavity 110, andfirst 2730 b and second 2730 c conductive traces in the cavity 110 thatare configured to connect to at least one semiconductor light emittingdevice 150 that is mounted in the cavity. As shown in FIG. 27, thetraces can provide series connection between the semiconductor lightemitting devices. However, parallel and/or series/parallel oranti-parallel connections also may be provided. It will be understoodthat larger or smaller numbers of semiconductor light emitting devicesand/or cavities may be provided in other embodiments.

Still referring to FIG. 27, a flexible film 1420 that includes anoptical element 1430 such as a lens therein, is provided on the firstmetal face 100 a, wherein a respective optical element 1430 extendsacross a respective cavity 110. Various embodiments of flexible films1420 and optical elements 1430 may be provided as was describedextensively above. Moreover, phosphor may be integrated as was describedextensively above. In other embodiments, discrete lenses 170 also may beprovided, instead of the flexible film 1420 containing optical elements1430. In some embodiments, the conductor 130 is connected to anintegrated circuit 2710, such as the light emitting device driverintegrated circuit, on the solid metal block 110. In some embodiments, asemiconductor light emitting package of FIG. 27 can be configured toprovide a plug-in substitute for a conventional light bulb.

FIG. 28 is a perspective view of embodiments according to FIG. 27. Asshown in FIG. 28, an array of cavities 110 that are connected by aconductive layer 130 may be provided on the first face 100 a of a solidmetal block 100. In FIG. 28, a uniformly spaced 10% 10 array of cavitiesand a corresponding 10% 10 array of optical elements 1430 on a flexiblefilm 1420, is shown. However, larger or smaller arrays may be providedand the arrays may be circular, randomly spaced and/or of otherconfiguration. Moreover, nonuniform spacing may be provided in some orall portions of the array of cavities 110 and optical elements 1430.More specifically, uniform spacing may promote uniform light output,whereas nonuniform spacing may be provided to compensate for variationsin heat dissipation abilities of the heat sink fins 190 across variousportions of the solid metal block 100.

It will also be understood that embodiments of FIGS. 27 and 28 may becombined in various combinations and subcombinations with any of theother embodiments described herein.

FIG. 29 is a side cross-sectional view of other embodiments of thepresent invention. In these embodiments, the first metal face 100 afurther includes a plurality of pedestals 2900 therein, and a respectiveone of the plurality of cavities 110 is in a respective one of theplurality of pedestals 2900. The insulating layer 120 and conductivelayer 130 are not illustrated in FIG. 29 for the sake of clarity.Multiple cavities 110 also may be provided in a given pedestal 2900 inother embodiments. In embodiments of FIG. 29, the flexible film 1420′includes a plurality of optical elements 1430′, such as lenses, arespective one of which extends across a respective pedestal 2900 andacross a respective cavity 110. It will be understood that larger orsmaller numbers of semiconductor light emitting devices and/or cavitiesmay be provided in other embodiments.

By providing pedestals 2900 according to some embodiments of the presentinvention, the light emitting devices 150 may be placed closer to theradial center of the optical elements 1430′, to thereby allow theuniformity of emissions to be enhanced. It will also be understood thatembodiments of FIG. 29 may be provided with discrete optical elements,such as lenses, a respective one of which spans across a respectivepedestal 2900 and cavity 110, and that embodiments of FIG. 29 may becombined with any combination or subcombination of the other embodimentsthat were described above.

FIG. 30 is a flowchart of steps that may be performed to packagesemiconductor light emitting devices according to various embodiments ofthe present invention. Methods of FIG. 30 may be used to package one ormore semiconductor light emitting devices, to provide structures thatwere described in any of the preceding figures.

As shown in FIG. 30 at Block 3010, a solid metal block includingcavities and heat sink fins is fabricated, as was described extensivelyabove. An insulating layer is formed on at least a portion of the solidmetal block, for example on the first metal face thereof, at Block 3020,as was described extensively above. At Block 3030, a conductive layer isformed on the insulating layer. The conductive layer may be patterned toprovide a reflective coating in the cavities, and first and secondconductive traces on the first face that extend into the cavities, aswas described extensively above. At Block 3040, at least onesemiconductor light emitting device is mounted in a respective cavity,and electrically connected to the first and second conductive traces inthe respective cavity, as was described extensively above. At Block3050, an optical coupling medium may be added, as was described above.At Block 3060, a lens, optical element and/or flexible film is placed onthe first face, as was described extensively above. In otherembodiments, through holes, reflector layers and/or other structuresthat were described extensively above, also may be provided.

It also will be noted that in some alternate implementations, thefunctions/acts noted in the blocks of FIG. 30 may occur out of the ordernoted in the flowchart. For example, two blocks shown in succession may,in fact, be executed substantially concurrently, or the blocks maysometimes be executed in the reverse order, depending upon thefunctionality/acts involved.

Additional discussion of various embodiments of the present inventionnow will be provided. Embodiments of the present invention can provide athree-dimensional topside and backside topology on solid metal blocks,to thereby provide integral reflector cavities and integral heat sinksall in one piece. The integrated optical cavities may facilitatealignment and ease of manufacturing. The integral heat sink may enhancethermal efficiency. By adopting a three-dimensional topside topology toform reflectors for the LEDs, the need to individually package the LEDs,mount the package to a heat sink and add the desired drive electronicsmay be eliminated, according to some embodiments of the presentinvention. Thus, a “chip on integral reflector heat sink” may beprovided as a single component. High optical efficiency and high thermalefficiency thereby may be provided. Adding the drive circuitry canprovide a complete solution for a functional luminary that may only needa source voltage and a final luminary housing.

Any shape or density device may be provided. For example, one may desireto have a high lumen intensity (lumen per square millimeter), or one maydesire to enhance or optimize the thermal efficiency by distributing thecavity layout. A high density embodiment may have four high power LEDssuch as are marketed under the designation XB900 by Cree, Inc., theassignee of the present invention, to provide a 2% 2 array, while adistributed thermal approach may have 100 lower power LEDs, such as aremarketed under the designation XB290 by Cree, Inc., the assignee of thepresent invention, to provide a 10% 10 array, to achieve the same lumenoutput. The XB900 and XB290 devices are described in a product brochureentitled Cree Optoelectronics LED Product Line, Publication CPR3AX, Rev.D, 2001-2002. Other devices that are described in this product brochure,such as XT290, XT230 and/or other devices from other manufacturers alsomay be used.

As was described above, the optical cavities may be either recessed ormay be provided as optical cavities in pedestals. The conductive layercan provide die-attach pads and wire bond pads. Separate traces may beprovided for red, green or blue LEDs, or all the LEDs may be connectedin series or in parallel.

Embodiments of the present invention can provide a configuration thatmay be able to replace a standard MR16 or other light fixture. In someembodiments, 6.4 watts input may provide about 2.4 watts of opticalpower and 4 watts of heat dissipation.

In the drawings and specification, there have been disclosed embodimentsof the invention and, although specific terms are employed, they areused in a generic and descriptive sense only and not for purposes oflimitation, the scope of the invention being set forth in the followingclaims.

1. A mounting substrate for a semiconductor light emitting devicecomprising: a solid metal block including first and second opposingmetal faces; an insulating layer on the first metal face; a conductivelayer on the insulating layer that is patterned to provide first andsecond conductive traces that are configured to connect to at least onesemiconductor light emitting device that is mounted on the first metalface; and the second metal face including therein a plurality of metalheat sink fins.
 2. A mounting substrate according to claim 1 wherein thesolid metal block comprises a solid aluminum block and wherein theinsulating layer comprises aluminum oxide.
 3. A mounting substrateaccording to claim 1 wherein the solid metal block comprises a solidsteel block and wherein the insulating layer comprises ceramic.
 4. Amounting substrate according to claim 1 wherein the solid metal blockincludes a through hole therein that extends from the first face to thesecond face and wherein the through hole includes a conductive viatherein that is electrically connected to the first or second conductivetraces.
 5. A mounting substrate according to claim 1 in combination withat least one semiconductor light emitting device that is mounted on thefirst metal face and electrically connected to the first and secondconductive traces.
 6. A mounting substrate according to claim 5 infurther combination with a flexible film that includes an opticalelement therein on the first metal face, wherein the at least onesemiconductor light emitting device is between the optical element andthe first metal face.
 7. A mounting substrate according to claim 6wherein the optical element comprises a lens.
 8. A mounting substrateaccording to claim 7 in further combination with a coating comprisingphosphor on the lens.
 9. A mounting substrate according to claim 7wherein the lens includes phosphor dispersed therein.
 10. A mountingsubstrate according to claim 1 further comprising an integrated circuiton the solid metal block that is electrically connected to the first andsecond conductive traces.
 11. A mounting substrate according to claim 1further comprising a semiconductor light emitting device driverintegrated circuit on the solid metal block that is electricallyconnected to the first and second conductive traces.
 12. A mountingsubstrate for a semiconductor light emitting device comprising: a solidmetal block including first and second opposing metal faces; aninsulating layer on the first metal face; a conductive layer on theinsulating layer that is patterned to provide first and secondconductive traces on the first metal face; at least one semiconductorlight emitting device that is mounted on the first metal face andelectrically connected to the first and second conductive traces; and aflexible film that includes an optical element therein on the firstmetal face, wherein the at least one semiconductor light emitting deviceis between the optical element and the first metal face.
 13. A mountingsubstrate according to claim 12 wherein the solid metal block comprisesa solid aluminum block and wherein the insulating layer comprisesaluminum oxide.
 14. A mounting substrate according to claim 12 whereinthe solid metal block comprises a solid steel block and wherein theinsulating layer comprises ceramic.
 15. A mounting substrate accordingto claim 12 wherein the solid metal block includes a through holetherein that extends from the first face to the second face and whereinthe through hole includes a conductive via therein that is electricallyconnected to the first or second conductive traces.
 16. A mountingsubstrate according to claim 12 wherein the optical element comprises alens.
 17. A mounting substrate according to claim 16 in furthercombination with a coating comprising phosphor on the lens.
 18. Amounting substrate according to claim 16 wherein the lens includesphosphor dispersed therein.
 19. A mounting substrate according to claim16 wherein the second metal face includes therein a plurality of metalheat sink fins.
 20. A mounting substrate according to claim 12 furthercomprising a semiconductor light emitting device driver integratedcircuit on the solid metal block that is electrically connected to thefirst and second conductive traces.